1. Field of the Invention
The present invention relates generally to a method of treatment of viral diseases using 6-amino-1,2-benzopyrones as antiviral agents. More specifically, it relates to the use of 6-amino-1,2-benzopyrones, their homologues and salts, in suppressing and inhibiting the growth of viruses in a mammalian host. These compounds are particularly effective inhibitors of human immunodeficiency virus, herpes simplex virus and cytomegalovirus and are therefore particularly useful for treatment of AIDS, herpetic episodes and cytomegaloviral infections. Moreover, these compounds have very low, if any, toxicity.
2. The State of Art and Related Disclosures
Viral infections became one of the most serious problem of the modern society. Their high degree of infectiousness and a fast reproduction cycle within the host organism, combined with essentially no effective treatment available aside of largely toxic desoxyribonuclotide homologs, make the viruses a nuisance and health hazard which the human population encounters on daily basis.
Viruses are intracellular parasitic molecular particles consisting essentially of a central core nucleic acid surrounded by an outer cover of protein. For their reproduction, viruses are wholly dependent on the host cells.
Several hundred different viruses are know to cause infection in man. Because of their wide prevalence, the viral diseases create important medical and public health problems. Included among them is the most common of all viral diseases, the influenza which alone is responsible for one billion episodes of disease every year in the United States alone, or such highly infectious viral diseases as measles, chickenpox, rabies, herpetic viral diseases, cytomegaloviruses and human immunodeficiency virus causing AIDS. All these viruses are spread quickly by man himself, mainly via respiratory and enteric excretions or by contact. Moreover, some of the viruses are very resistant to any treatment and some of them, for example herpes simplex viruses or cytomegalovirus, once inside the body, may remain forever in a dormant state until the resistance is weakened. The others, such as human immunodeficiency virus is nearly always fatal.
There is no simple treatment of viral diseases. They are not susceptible to antibiotics and there is no other available treatment of viral diseases other than by chemotherapy which inhibits viral replication in the host cells. The Merck Manual, 170 (1982). Examples of these chemical agents are idoxuridine (IDU) useful for treatment of herpes simplex keratitis and methisazone active against influenza A virus. The other known viral replication inhibitors are acyclovir, ribavirin, vidarabine, gancyclovir, adenine arabinoside (ARA-A) and AZT. These, and other viral replication inhibitors, however, are known to be cytotoxic, hepatotoxic, neurotoxic, nephrotoxic and were shown to have teratogenic effects. Virus Diseases, 1-6 (1978), Crown Publishers, N.Y.
Thus it would be highly desirable to have available an effective and yet nontoxic treatment of viral diseases.
Human immunodeficiency virus (HIV) infections presently constitute one, if not the most pressing health hazard worldwide. Known as acquired immunodeficiency syndrome (AIDS), HIV infections are almost always fatal because due to a weakened immunoresistance, they are quickly accompanied by opportunistic infections, malignancies and neurologic lesions leading to an early death.
HIV term encompasses a group of retroviruses known and termed human T-lymphotropic virus Type III, (HTLV-III), lymphadenopathy-associated virus (LAV) and retrovirus (ARV).
Retroviruses contain an enzyme called reverse transcriptase that can convert viral RNA in the cytoplasm into DNA, which may replicate from extrachromosomal sites or move into the cell nucleus where it becomes part of the host cell DNA. These integrated viral genes are duplicated with normal cellular genes, and all progeny of the originally infected cells will contain the viral genes. Expression of the viral genes for some retroviruses may be oncogenic, converting the cell into a cancer, or may have other pathologic effects which may alter normal cell function or produce cell death.
AIDS patients experience a broad spectrum of acute or chronic clinical problems such as lymphadenopathy, weight loss, intermittent fever, malaise, lethargy, chronic diarrhea, lymphopenia or, anemia, with full blown AIDS syndrome consisting of any of the above symptoms combined with the whole scale of opportunistic infections, such as pneumocystis carinii pneumonia, candidiasis, mycobacterial infections, cytomegalovirus or herpes simplex virus infections, to name a few, or with secondary cancers, such as Kaposi's sarcoma and various lymphomas. These opportunistic and secondary infections cause more than 90% fatality in AIDS patients.
There is no effective treatment for AIDS other than that of the opportunistic infections, neoplasms and other complications. Available cytostatic (AZT) and antiviral (acyclovir) drugs are mostly extremely toxic and consequently cause severe side effects. Because of its fatality and because of the lack of treatment for AIDS patients, enormous efforts are aimed at development of effective anti-HIV drugs or vaccines. The most promising of all those currently investigated seem to be antiviral drugs which may somehow inhibit the viral reproduction enzyme, reverse transcriptase. The Merck Manual, 15th Ed., 288 (1987).
To provide an effective and yet non-toxic antiviral drug which would effect the reproduction of HIV would thus be of extreme importance and life saving measure for many thousands of AIDS victims.
Herpes simplex virus type-1 and 2 similarly are wide spread infections. They may occur in AIDS patients as one of the opportunistic infections. HSV-2 has been related to the development of uterine cancer.
Herpes simplex, also called fever blister and cold sore is one of the most prevalent viral infection. The infecting agent is the relatively large herpes simplex virus herpesvirus hominis (HVH). There are two HVH strains. Type-1 strain (HSV-1) commonly causes herpes labialis located on a lip, and keratitis, an inflammation of the cornea. Type-2 is usually located on or around genital area and is generally transmitted primarily by direct contact with herpetic sore or lesions.
Estimated frequency and location of oral (HSV-1) and genital (HSV-2) infections are about half million of primary cases of type-1 per year, with 98 million of recurrent cases per year in the United States alone. Of the genital HSV-2 cases, there are around 500,000 cases of primary genital herpes with 3-9 million of recurrent cases per year in the United States. Living With Herpes, 1-11, (1983), Doubleday and Company, N.Y.
Herpes simplex virus is very infectious and is rapidly and easily transferable by contact. There is no specific therapy to this extremely painful viral infection. Corticosteroids, if given early, may relieve pain in severe cases. Aspirin and other anti-inflammatories or antiviral agents systemically may alleviate the pain. However, these agents have the same undesirable side effects as those discussed previously. Treatment of HSV infections is primarily by systemic administration of antiviral drugs, such as for example with highly cytotoxic IDU and trifluridine (TFT), with ARA-A, and with acyclovir or bromovinyldeoxyuridine semi-specific enzyme inhibitors of virus replication.
Since the primary route of administration of these agents is systemic, severe side effects were shown to accompany such treatments. Moreover, these agents are not selective inhibitors of the herpes simplex virus replication but effect also a replication of normal cells. Therefore, when used in doses large enough to seek and destroy all the active herpes viruses dormant in the sensory ganglia, these compounds may also be highly disruptive to the normal DNA in the host cells in which the virus multiplies. This is a very undesirable effect since the replication of normal cells is also effected.
Thus, it would be advantageous to have available nontoxic treatment of HSV infections.
Cytomegalovirus (CMV) is often a dangerous co-infection of HIV. The human CMVs are a subgroup of highly infectious agents having the propensity for remaining latent in man. CMVs are very common among the adult population and as many as 90% of adults have been exposed to and experienced CMVs infections. CMVs are normally present in body liquids such as blood, lymph, saliva, urine, feces, milk, etc. Congenital CMV infections may cause abortion, stillbirth, postnatal death from hemorrhage, anemia or severe hepatic or CNS damage. In adults, CMV infection may be asymptomatic but may also cause hepatitis, atypical lymphocytosis or blindness. Particularly dangerous are CMS infections afflicting AIDS patients, where CMV may cause pulmonary, gastrointestinal or renal complications.
There is no specific therapy for CMVs. Contrary to the HSV, CMV is resistant to acyclovir, a potent and very toxic anti-viral drug and to other known antiviral drugs.
Thus, it would be extremely advantageous to have available the drug which would effectively inhibit CMV infections.
The existing chemotherapeutical treatment of the most viral infections is thus mostly limited to very toxic agents and antivirals.
It is therefore a primary object of this invention to provide a non-toxic, highly effective antiviral drugs. 6-amino-1,2-benzopyrones (6-ABP) seem to be a group of such prototype antiviral drug.
This drug, (6-ABP) has been now found to be an agent of remarkably low toxicity, yet highly effective viral inhibitor in cell cultures and in human blood. Its antiviral spectrum appears to be particularly useful for treatment of the most dangerous viral infections, such as above described infections caused by HIVs, CMVs and HSVs. However it may be equally effective in treatment of other viral diseases.
6-aminobenzopyrone has been known and described in J. Pharm. Soc. Jap., 498:615-628 (1923). However, only scarce medicinal use of this substance has been reported, although the testing was done for sedative and hypnotic effects (J. Pharm. Soc. Japan, 73:351 (1953) and Ibid, 74:271 (1954). Hypothermal action was studied but it was found that 6-amino group decreased the hypothermal effect Yakugaku Zasshi, 78:491 (1958). Some antipyretic, hypnotic, hypotensive and adrenolytic action was reported, Ibid, 83:1124 (1963).
Related molecule, 1,2-benzopyrone (coumarin) was shown to be an inhibitory ligand of adenosinediphosphoribose transferase (ADPRT), a DNA-binding nuclear protein present in neoplastic cells (Proc. Nat. Acad. Sci. (USA), 84:1107 (1987)).
Further research showed that 6-ABP is specifically binding to ADPRT at the same site that also binds catalytically effective DNA termini. Thus, both 6-ADP and DNA compete for the same site on ADPRT. These results were disclosed in FEBS Lett., 212:73 (1987), where the biological role of ADPRT was studied extensively with the aid of synthetic ligands of ADPRT and shown to inhibit DNA proliferation, particularly in tumorigenic cells.
The primary object of this invention is the discovery that 6-ABPs, previously known to have only limited biological utility, are specific, selective, potent and non-toxic antiviral agents. The testing of these compounds on various virally infected cultures, including HIV infected human lymphoblasts, showed that 6-ABP are particularly useful for inhibition of HIV, HSV and CMV replication.